Automotive air conditioning systems incorporate numerous fluid tight connections between refrigerant lines and other components, such as compressors, condensers, evaporators, accumulator canisters, as well as other refrigerant lines. These fluid connections have to be made during installation and broken during servicing, in very confined underhood spaces. Historically, most such connections were made with threaded hose type fittings, which require a good deal of space within which to swing a tool over a wide arc, around the axis of the line. Increasingly, such connections are being made with block type connectors, in which at least one block welded or brazed to the end of the refrigerant line is attached by a bolt that runs through the block, offset to the side of, and parallel to, the axis of the line. This type of connector generally requires less tool access space, since the tool that drives the bolt fits in close to the line. It also generally gives a good, leak free seal, the compression of which is controlled simply within less space than a conventional hose type fitting tool would require.
A block type fitting can be used to connect two lines to one another, end to end. In that case, two mating blocks, one fixed to the end of each line, are fastened together with a bolt that runs through both blocks, parallel to the common axis of the lines. Neither block is symmetric to the axis. Rather, each has a lobe offset to the side, through which the bolt extends. A block fitting can also be used to fluidly connect a single line to a port that opens through the wall of another component, such as a condenser tank or an accumulator canister. If the wall through which the port opens is thick enough, then the bolt can be threaded directly into it, and only one connector block, then one fixed to the end of the refrigerant line, is needed. An example may be seen in U.S. Pat. No. 5,191,775, in which an accumulator canister has an end cap thick enough to accept the bolt directly.
If the port to which the line is to be connected is too thin to accept the bolt directly, it must be locally reinforced surrounding the port. For example, in co-assigned U.S. Pat. No. 5,163,716, a line 12 is to be connected to a port P in the thin side wall of a condenser tank C. A secondary connector block 14 is attached to the tank C at the port P, with a robust weld bead 20. The secondary connector block 14 is thick enough to accommodate a threaded bolt hole 22. However, it should be noted that the refrigerant line 12 runs perpendicular to the port P, not concentric to it. The reason for this is that if the line 12 were to run concentric to the port P, then block 14 would have to have a lobe offset to the side of port P to accommodate the bolt 16. Such a side lobe interrupts the cylindrical symmetry of the block, and overhangs the wall surface to which it is welded, obstructing access to the welding tool. It happens to be space effective to plumb the condenser tank C with a refrigerant line that is perpendicular to the port, so there is no problem in that situation.
In some situations where it is desired to use a block connector, however, it is necessary both to run the line concentric to the port to which it is connected, and the wall surface is too thin to accept a threaded bolt directly. It is very difficult to weld a connector block with an overhanging side lobe to the component wall in such a situation, because of the obstructed welding tool access noted above.